An entrenched river is a river that is confined to a canyon or gorge, usually with a relatively narrow width and little or no flood plain, and often with meanders worn into the landscape. Such rivers form when the base level of erosion is rapidly lowered, so that the river begins downcutting into its channel faster than it can change course (which rivers normally do on a constant basis). This may occur due to tectonic uplift of the region, a lowering of the oceans, the collapse of a moraine-dammed lake downstream, or by capture of the river by another.
Meanders in these landscapes are collectively known as 'incised meanders and come in two forms. An ingrown meander is one where incision is slow and lateral erosion takes place resulting in an asymmetric valley. This resembles an exaggerated un-incised meander. The other sort is an entrenched meander, here rapid incision occurs creating a more symmetrical valley with a gorge like appearance. Both types are due to meanders becoming established before Rejuvenation.
Examples of incised meanders may be seen in the Snake River Canyon in southern Idaho, and in many canyons of the Colorado Plateau.
Famous quotes containing the words entrenched and/or river:
“He began therefore to invest the fortress of my heart by a circumvallation of distant bows and respectful looks; he then entrenched his forces in the deep caution of never uttering an unguarded word or syllable. His designs being yet covered, he played off from several quarters a large battery of compliments. But here he found a repulse from the enemy by an absolute rejection of such fulsome praise, and this forced him back again close into his former trenches.”
—Sarah Fielding (1710–1768)
“This ferry was as busy as a beaver dam, and all the world seemed anxious to get across the Merrimack River at this particular point, waiting to get set over,—children with their two cents done up in paper, jail-birds broke lose and constable with warrant, travelers from distant lands to distant lands, men and women to whom the Merrimack River was a bar.”
—Henry David Thoreau (1817–1862)